Sunday, November 18, 2012

Building bumpers

This weekend I built myself some bumpers, for my yard tracks and spurs. I made a total of five Hayes style bumpers. I began by searching the Internet for some pictures and information on bumpers. On the Western-Cullen-Hayes, Inc. web page I stumbled upon this Bumping Posts Facts and Dimensions brochure. Perfect, with pictures, explanatory text and dimensions. Everything I needed.

I first tried to build a free-standing bumper, with the intention of installing on the track when it was complete. It turned out that was not that easy. For starters, it was difficult to get the correct dimensions. Not only should the bumper if possible have the same dimensions as a real bumping post, as specified in the brochure. It should also fit the model track. These two constraints turned out to not be 100% compatible. It was also hard to get the bumper square and even. Anyway, this was what I ended up with, built from different pieces of styrene.

It looks quite alright, and served part of its purpose; I got the general hang of how to build a bumper. But I decided to switch methods and build the bumpers in place instead.

So I started by gluing pieces of styrene angle along two ties on each track. Those are the reinforcement bars extending in under the rails, that help keeping the bumper in place when hit by a car.

Next I cut the so called compression members from .080" (2mm) styrene H-column. I cut them at an angle, beveled the ends and glued them together two and two.

Then I glued the paired compression members to the track, resting on the earlier installed reinforcements bars. I used pieces of MDF board as supports while the glue set.

And this is what it looked like so far, with the temporary supports removed.

Using a car to test fit the height. The head should eventually end up at the same height as the coupler on the car.

Next it was time for the tension members.I fabricated those out of a single piece of .010x.060" (0.25x1.5mm) styrene strip, which I first glued to the top of the compression members and then bent down to the track. To make the strip really bend, instead of breaking, I put on dabs on styrene cement where the bends would go. This softens the styrene and makes it possible to bend.

Last, I made the head from .080" (2mm) square rod and some .01x.125" (0.3x3.2mm) styrene strip. I really needed a rod with a triangular profile, to get the front surface of the head (where the cars hit) vertical. Since I only had square rod at hand, I had to file and shape it to make its profile triangular.

Here the heads are mounted, along with some "bolt bars", to make it believable that the bumper is actually attached to the rails.

Next the bumpers need some paint, and weathering.

Thanks for watching.

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